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examBoard: Pearson Edexcel
examType: IGCSE
lessonTitle: Homeostasis Principles
Our bodies are constantly working to keep things just right inside - not too hot, not too cold, not too acidic, not too alkaline. This balancing act is called homeostasis and it's essential for our survival. Without it, our cells wouldn't be able to function properly and our bodies would quickly fail.
Key Definitions:
Our cells need specific conditions to work properly. Enzymes that control chemical reactions in our bodies only function within narrow ranges of temperature and pH. If these conditions change too much, the enzymes stop working and cellular processes break down. Homeostasis keeps our internal environment stable so our cells can do their jobs.
Our bodies maintain many factors at steady levels, including:
Homeostasis works through control systems that detect changes and correct them. These systems have three main parts that work together like a team.
These are specialised cells that detect changes in the internal environment. They act like sensors, monitoring conditions and sending signals when things change. For example, temperature receptors in your skin detect when you're getting too hot or cold.
Usually part of the brain or spinal cord, these receive information from receptors and decide what needs to be done. The hypothalamus is a key processing centre for many homeostatic processes, like a control room for your body.
These are organs or tissues that carry out the necessary actions to restore balance. Muscles and glands are common effectors. For example, sweat glands produce sweat to cool you down when you're too hot.
Most homeostatic mechanisms use negative feedback. This means that when a change occurs, the body responds in the opposite direction to bring conditions back to normal.
Imagine your body temperature starts to rise above 37°C:
This is called negative feedback because the response negates (opposes) the original change. It's like a thermostat in your home that turns on the air conditioning when it gets too warm, then switches it off when the temperature is back to normal.
Blood glucose regulation is a perfect example of homeostasis in action. After eating, blood glucose levels rise. This triggers the pancreas to release insulin, which helps cells take up glucose from the blood, lowering blood glucose levels back to normal.
In Type 1 diabetes, the pancreas doesn't produce enough insulin. Without this negative feedback mechanism, blood glucose levels remain dangerously high after eating. People with diabetes need to inject insulin to replace this broken homeostatic mechanism.
This shows what happens when homeostatic mechanisms fail - the internal environment becomes unstable, leading to serious health problems.
The human body maintains a core temperature of around 37°C. When we get too hot or too cold, our bodies respond in several ways:
Our bodies need to maintain the right amount of water to function properly. This involves balancing water intake with water loss:
Homeostasis isn't just a biological concept - it's essential for our survival. Without these finely tuned control systems:
Many diseases result from failures in homeostatic mechanisms. Understanding how homeostasis works helps us understand how these diseases develop and how they can be treated.
When you exercise intensely, your body faces several challenges to homeostasis:
Athletes' bodies become more efficient at maintaining homeostasis through training. They sweat more efficiently, their bodies become better at regulating temperature and they can maintain stable blood glucose levels for longer periods. This is why trained athletes can perform at higher intensities for longer than untrained individuals.
Homeostasis is the maintenance of a stable internal environment despite changes in the external environment. It works through control systems involving receptors, processing centres and effectors, usually using negative feedback mechanisms. Key examples include temperature regulation, blood glucose control and water balance. When homeostatic mechanisms fail, illness can result, highlighting the critical importance of these systems for our survival.
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